Set Channel Message Reaction

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover idempotency, non-destructiveness, and mutating behavior. The description adds useful behavioral context by specifying supported Unicode emoji and named reactions, and by calling out that replies can be reacted to. No contradiction with annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences with no fluff. The main action is front-loaded, and the additional reaction-type and reply details are placed efficiently.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a mutation tool with six parameters, the description covers the key behavioral aspects: channel targeting, reply support, and acceptable reaction formats. With full schema coverage and annotations, little critical information is missing, though it does not mention return behavior or explicit error cases.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, providing baseline 3. The description adds meaning beyond the schema by giving concrete named reactions and confirming replyId is used for replying, which enriches understanding of reactionType and replyId.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses a specific verb and resource: 'Add a reaction to a message in a Teams channel.' The mention of 'Teams channel' and 'replies' clearly distinguishes this from sibling tools like set_chat_message_reaction and set_chat_read_state, and the supported reaction types are enumerated.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It provides clear context: this tool is for channel messages and can also react to replies. However, it does not explicitly mention when not to use it or name alternatives such as unset_channel_message_reaction for removing reactions or set_chat_message_reaction for chat messages.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.